Immunoassay by light scattering spectroscopy

Abstract

This inventin provides a means for determining the concentration of any of a wide range of antibody or antigen molecules with a high degree of specificity, accuracy and sensitivity. Antigen or antibody concentration is determined by effecting an agglutination reaction in a liquid medium and determining the mean diffusion constant of the agglutinated reaction product by quasi-elastic light scattering spectroscopy. The measured mean diffusion constant then is compared with a standard quantitative relationship between mean diffusion constant and concentration of the antigen or antibody being tested. By this means one may specifically ascertain the absolute concentration of the antigen or antibody in question in the sample being analyzed. In addition to detecting antigen or antibody molecules, the process of this invention can be used to determine the concentration of any substance capable of specifically promoting or inhibiting an agglutination reaction such as viruses, white blood cells or the like.

We claim: 
     
       1. The process for determining the concentration of a substance which promotes or inhibits an agglutination reaction which comprises: (a) determining the quantitative relationship between the mean diffusion constant of an agglutinated reaction product and the known concentration of the substance being tested using a fixed concentration of an agglutinant wherein the mean diffusion constant of the agglutinated reaction product is measured by quasi-elastic light scattering spectroscopy,   (b) mixing an unknown concentration of one or more dilutions of the substance being tested with the same agglutinant to form at least one agglutinated reaction product of the dilutions,   (c) determining the mean diffusion constant of the agglutinated reaction product of the dilutions by quasi-elastic light scattering spectroscopy and   (d) comparing the mean diffusion constant of the agglutinated reaction product obtained in step (c) with the quantitative relationship determined by step (a).   
     
     
       2. The process of claim 1 wherein the agglutinant comprises antigen-coated carrier particles. 
     
     
       3. The process of claim 1 wherein the agglutinant comprises antibody-coated carrier particles. 
     
     
       4. The process of claim 1 wherein the substance being tested is an antigen which first is mixed with a fixed concentration of its complementary antibody and combining the resultant mixture with a fixed concentration of said antigen coated on carrier particles. 
     
     
       5. The process of claim 1 wherein the substance being tested is an antibody which first is mixed with a fixed concentration of its complementary antigen and combining the resultant mixture with a fixed concentration of said antibody coated on carrier particles. 
     
     
       6. The process of claim 1 wherein the substance being tested is an antigen which is combined with a fixed amount of its complementary antibody. 
     
     
       7. The process of claim 1 wherein the substance being tested is an antibody which is combined with a fixed amount of its complementary antigen. 
     
     
       8. The process of claim 4 wherein the antigen is luteinizing hormone. 
     
     
       9. The process of claim 4 wherein the antigen is human chorionic gonadotropin. 
     
     
       10. The process of claim 3 wherein the substance being tested is luteinizing hormone. 
     
     
       11. The process of claim 3 wherein the substance being tested is human chorionic gonadotropin. 
     
     
       12. The process of claim 6 wherein the antigen is luteinizing hormone. 
     
     
       13. The process of claim 6 wherein the antigen is human chorionic gonadotropin. 
     
     
       14. The process of claim 1 wherein the substance being tested is a virus and the agglutinant comprises red blood cells. 
     
     
       15. The process of claim 1 wherein the substance being tested comprises an antibody to a virus and wherein the agglutinated reaction products are obtained by mixing said antibody with a fixed concentration of said virus to inactivate said antibody and adding a fixed concentration of red blood cells to said mixture to effect an agglutination reaction of said virus and said blood cells. 
     
     
       16. The process of claim 1 wherein lymphocyte cells obtained from one individual are used to agglutinate the substance being tested which comprises lymphocyte cells obtained from a second individual.